I notice a lot of wool longies/soakers etc are mutiple colors, its seems more common but I want solid colors like cream or beige, should I look at interlock instead? Also what is the softest wool? Cestari? What about best for crawlers? She not there yet just rolling but its coming!

Sustainablebabyish comes in solid colors and is very soft. Upcycled wool can usually be found in solid colors too. Interlock is stretchy and non-binding, but not as soft to the touch. I really like the durability of interlock. I've been stocking up on WCW shorties lately :)

Cestari fine is one of my most favorite yarn bases. It is SO soft. It seems to pill a bit, but is sturdy, so a sweater shaver cleans it up nicely. Also, I like Gaia and MMR. They are soft and sturdy as well. As far as solids, knitpicks.com wool of the Andes worsted weight works great, holds up very well and is super cheap. It's not overly soft, but does soften up with each washing. Any hand dyer could do simple solids or you could maybe search etsy for premade woolies in solid colors.